Metal-Free Tandem Oxidative Cyclization for the Synthesis of 1,2-Dihydropyridazines and Pyrazoles.

Mediated by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), a novel oxidative coupling of hydrazones and 1,3-diarylpropenes has been disclosed to generate appealing ß,γ-unsaturated hydrazones, which further undergo 5-exo-trig or 6-endo-trig cascade cyclization to give the respective 1,2-dihydropyridazines or pyrazoles selectively under metal-free conditions. The mechanisms of the coupling and subsequent cyclization are proposed.

Cytisine-Pterocarpan-Derived Compounds: Biomimetic Synthesis and Apoptosis-Inducing Activity in Human Breast Cancer Cells.

Cytisine-pterocarpan-derived compounds were biomimetically synthesized with (-)-cytisine and (-)-maackiain via a N,N-4-dimethyl-4-aminopyridine (DMAP)-mediated synthetic strategy in a mild manner. In the present study, tonkinensine B (4) was elaborated in good and high yields with the optimized reaction conditions. The in vitro cytotoxicity of compound 4 was evaluated against breast cancer cell lines and showed that 4 had a better cytotoxicity against MDA-MB-231 cells (IC50 = 19.2 µM). Depending on the research on cytotoxicities of 4 against RAW 264.7 and BV2 cells, it was suggested that 4 produced low cytotoxic effects on the central nervous system. Further study indicated that 4 demonstrated cytotoxic activity against MDA-MB-231 cells and the cytotoxic activity was induced by apoptosis. The results implied that the apoptosis might be induced by mitochondrion-mediated apoptosis via regulating the ratio of Bax/Bcl-2 and promoting the release of cytochrome c from the mitochondrion to the cytoplasm in MDA-MB-231 cells.

CDC Reaction and Subsequent Cyclization for the Synthesis of 2-Hydroxy-3-alkyl-1,4-naphthoquinones and Pyranonaphthoquinones.

The metal-free cross-dehydrogenative coupling (CDC) reaction and subsequent cyclization of 2-hydroxy-1,4-naphthoquinone (lawsone) and 1,3-diarylpropene promoted by DDQ has been developed. 2-Hydroxy-3-alkyl-1,4-naphthoquinones and pyranonaphthoquinones with potential pharmaceutical applications are obtained in moderate to good yields. The reaction is also compatible for 4-hydroxycoumarins.

Preparative Enantioseparation of ß-Substituted-2-Phenylpropionic Acids by Countercurrent Chromatography With Substituted ß-Cyclodextrin as Chiral Selectors.

Preparative enantioseparation of four ß-substituted-2-phenylpropionic acids was performed by countercurrent chromatography with substituted ß-cyclodextrin as chiral selectors. The two-phase solvent system was composed of n-hexane-ethyl acetate-0.10 mol L-1 of phosphate buffer solution at pH 2.67 containing 0.10 mol L(-1) of hydroxypropyl-ß-cyclodextrin (HP-ß-CD) or sulfobutylether-ß-cyclodextrin (SBE-ß-CD). The influence factors, including the type of substituted ß-cyclodextrin, composition of organic phase, concentration of chiral selector, pH value of the aqueous phase, and equilibrium temperature were optimized by enantioselective liquid-liquid extraction. Under the optimum separation conditions, 100 mg of 2-phenylbutyric acid, 100 mg of tropic acid, and 50 mg of 2,3-diphenylpropionic acid were successfully enantioseparated by high-speed countercurrent chromatography, and the recovery of the (±)-enantiomers was in the range of 90-91% for (±)-2-phenylbutyric acid, 91-92% for (±)-tropic acid, 85-87% for (±)-2,3-diphenylpropionic acid with purity of over 97%, 96%, and 98%, respectively. The formation of 1:1 stoichiometric inclusion complex of ß-substituted-2-phenylpropionic acids with HP-ß-CD was determined by UV spectrophotometry and the inclusion constants were calculated by a modified Benesi-Hildebrand equation. The results showed that different enantioselectivities among different racemates were mainly caused by different enantiorecognition between each enantiomer and HP-ß-CD, while it might be partially caused by different inclusion capacity between racemic solutes and HP-ß-CD.

Modeling the retention mechanism for high-performance liquid chromatography with a chiral ligand mobile phase and enantioseparation of mandelic acid derivatives.

The chromatographic retention mechanism describing relationship between retention factor and concentration of Cu(2+) (l-phenylalanine)2 using chiral ligand mobile phase was investigated and eight mandelic acid derivatives were enantioseparated by chiral ligand exchange chromatography. The relationship between retention factor and concentration of the Cu(2+) (l-phenylalanine)2 complex was proven to be in conformity with chromatographic retention mechanism in which chiral discrimination occurred both in mobile and stationary phase. Different copper(II) salts, chiral ligands, organic modifier, pH of aqueous phase, and conventional temperature on retention behavior were optimized. Eight racemates were successfully enantioseparated on a common reversed-phase column with an optimized mobile phase composed of 6 mmol/L of l-phenylalanine or N,N-dimethyl-l-phenylalanine and 3 mmol/Lof copper(II) acetate or copper(II) sulfate aqueous solution and methanol.

Chiral ligand exchange high-speed countercurrent chromatography: mechanism and application in enantioseparation of aromatic α-hydroxyl acids.

This work concentrates on the separation mechanism and application of chiral ligand exchange high-speed countercurrent chromatography in enantioseparation of ten racemic aromatic α-hydroxyl acids, including mandelic acid, 2-chloromandelic acid, 4-methoxymandelic acid, 4-hydroxymandelic acid, α-methylmandelic acid, 4-hydroxy-3-methoxy-mandelic acid, 3-chloromandelic acid, 4-bromomandelic acid, α-cyclopentylmandelic acid and α-cyclohexylmandelic acid, in which five of the racemates were successfully enantioseparated by analytical apparatus with an optimized solvent system. The two-phase solvent system was composed of butanol-water (1:1, v/v) or hexane-n-butanol-water (0.5:0.5:1, v/v), to which N-n-dodecyl-l-proline was added in the organic phase as chiral ligand and cupric acetate was added in the aqueous phase as a transition metal ion. Various influence factors in high-speed countercurrent chromatography were optimized by enantioselective liquid-liquid extraction. The separation mechanism for chiral ligand exchange high-speed countercurrent chromatography was proposed based on the results of present studies. Successful enantioseparations of 72mg of mandelic acid, 76mg of 2-chloromandelic acid and 74mg of 4-methoxymandelic acid were achieved individually with high resolution by preparative high-speed countercurrent chromatography. The HPLC purity of all enantiomers was over 96% with the recovery in the range of 82-90% from the collected fractions.

The coupling of tertiary amines with acrylate derivatives via visible-light photoredox catalysis.

Catalyzed by Ru(bpy)3(BF4)2, the photoredox coupling of tertiary amines with acrylate derivatives including Baylis-Hillman adducts under visible light irradiation was successfully established. The scope of the substrates was broad, and thus an array of γ-aminobutyric ester derivatives was obtained in moderate to good yields.

Anti-proliferative and apoptosis-inducing effects of camptothecin-20(s)-O-(2-pyrazolyl-1)acetic ester in human breast tumor MCF-7 cells.

Camptothecin-20(s)-O-(2-pyrazolyl-1)acetic ester (CPT6) is a novel semi-synthetic analog of camptothecin. In a previous report, CPT6 possessed higher cytotoxic activity in vitro towards human breast tumor MCF-7 cells than topotecan. In this study, the antitumor activity of CPT6 on the human breast tumor MCF-7 cell line was analyzed using the MTT method. The underlying mechanism of CPT6 action was investigated by analyzing the cell cycle distribution, apoptotic proportion, changes in mitochondrial membrane potential, and intracellular Ca2+ concentration using flow cytometry. Nuclear and mitochondrial morphologies were also observed by laser scanning confocal and transmission electron microscopy. DNA damage was observed in MCF-7 cells treated with CPT6. Low-dose CPT6 had a significant cytotoxic effect and could inhibit proliferation and induce apoptosis in MCF-7 cells, possibly through cell nucleus fragmentation and DNA damage. CPT6 thus appears to display potent antitumor activity against human breast tumor MCF-7 cells via the induction of apoptosis, and may be a useful alternative drug for breast cancer therapy.

Discrimination of Dendrobium officinale and its common adulterants by combination of normal light and fluorescence microscopy.

The stems of Dendrobium officinale Kimura et Migo, named Tie-pi-shi-hu, is one of the most endangered and precious species in China. Because of its various pharmacodynamic effects, D. officinale is widely recognized as a high-quality health food in China and other countries in south and south-east Asia. With the rising interest of D. officinale, its products have a high price due to a limited supply. This high price has led to the proliferation of adulterants in the market. To ensure the safe use of D. officinale, a fast and convenient method combining normal and fluorescence microscopy was applied in the present study to distinguish D. officinale from three commonly used adulterants including Zi-pi-shi-hu (D. devonianum), Shui-cao-shi-hu (D. aphyllum), Guang-jie-shi-hu (D. gratiosissimum). The result demonstrated that D. officinale could be identified by the characteristic "two hat-shaped" vascular bundle sheath observed under the fluorescence microscopy and the distribution of raphides under normal light microscopy. The other three adulterants could be discriminated by the vascular bundle differences and the distribution of raphides under normal light microscopy. This work indicated that combination of normal light and fluorescence microscopy is a fast and efficient technique to scientifically distinguish D. officinale from the commonly confused species.

Synthesis and biological activity of some bile acid-based camptothecin analogues.

In an effort to decrease the toxicity of camptothecin (CPT) and improve selectivity for hepatoma and colon cancer cells, bile acid groups were introduced into the CPT 20 or 10 positions, resulting in the preparation of sixteen novel CPT-bile acid analogues. The compounds in which a bile acid group was introduced at the 20-hydroxyl group of CPT showed better cytotoxic selectivity for human hepatoma and colon cancer cells than for human breast cancer cells. Fluorescence microscopy analysis demonstrated that one compound (E2) entered human hepatoma cells more effectively than it did human breast cancer cells. Compound G4 exhibited the best anti-tumour activity in vivo. These results suggested that introduction of a bile acid group at the 20-position of CPT could decrease toxicity in vivo and improve selectivity for hepatoma cells.

Coumarins from Edgeworthia chrysantha.

A new coumarin, edgeworic acid (1), was isolated from the flower buds of Edgeworthia chrysantha, together with the five known coumarins umbelliferone (2), 5,7-dimethoxycoumarin (3), daphnoretin (4), edgeworoside C (5), and edgeworoside A (6). Their structures were established on the basis of spectral data, particularly by the use of 1D NMR and several 2D shift-correlated NMR pulse sequences (1H-1H COSY, HSQC and HMBC), in combination with acetylation reactions.

A new furolactone-type lignan from Lycium chinense.

The phytochemical investigation of extracts from the root barks of Lycium chinense yielded a new furolactone-type lignan, lyciumin (1). Its structure and absolute configurations were established on the basis of spectral data, particularly by the use of 1D NMR, 2D shift-correlated NMR pulse sequences ((1)H-(1)H COSY, HSQC, HMBC and ROESY) and CD spectra.

Norlignans from Asparagus cochinchinensis.

A new norlignan glycoside, named iso-agatharesinoside (2), and its aglycone, iso-agatharesinol (1), were isolated from the tuberous roots of Asparagus cochinchinensis. Their structures were established on the basis of spectral data, particularly by the use of 1D NMR and several 2D shift-correlated NMR pulse sequences (1H-1H COSY, HSQC, HMBC and ROESY).

Metal-free synthesis of allylic amines by cross-dehydrogenative-coupling of 1,3-diarylpropenes with anilines and amides under mild conditions.

Dehydrogenative cross-coupling reaction of primary anilines, secondary anilines, carboxamides, and sulfonamides with 1,3-diarylpropenes to form a series of allylic amines promoted by DDQ have been realized. Both monoallylation and diallylation products can be selectively synthesized when primary anilines are used as the starting materials. The method may provide a wide scope of allylamines in scientific research including biologically active compound library construction.

Highly stereoselective synthesis of cis-ß-enaminones mediated by diethyl azodicarboxylate.

Promoted by diethyl azodicarboxylate, a novel and highly stereoselective synthesis of cis-ß-enaminones via oxidative dehydrogenation and hydration of the substituted propargylamines was realized. The possible mechanism was also proposed.

Two phthalide dimers from the radix of Angelica sinensis.

The phytochemical investigation of extracts from the radix of Angelica sinensis yielded a new phthalide dimer, 3,3'Z-6.7',7.6'-diligustilide, along with a known dimer, levistolide A. Their structures were established on the basis of spectral data, particularly using 1D-NMR and several 2D shift-correlated NMR pulse sequences (¹H-¹H COSY, HSQC, HMBC and NOESY).

CuCl/CCl(4)-promoted convenient synthesis of sulfonyl amidines from tertiary amines and sulfonyl azides.

Promoted by CuCl/CCl(4), a variety of sulfonyl azides and tertiary amines were successfully coupled to give sulfonyl amidine derivatives in good to excellent yields. A possible mechanism for this reaction is discussed.

Propargylation of 1,3-dicarbonyl compounds with 1,3-diarylpropynes via oxidative cross-coupling between sp3 C-H and sp3 C-H.

A highly efficient oxidative-coupling reaction between diarylpropargylic sp(3) C-H and active methylenic sp(3) C-H was achieved with DDQ as oxidant. The reaction afforded a direct method for the propargylation of 1,3-dicarbonyl compounds, thus providing a concise synthesis of the corresponding products.

Copper-catalyzed highly efficient multicomponent reactions: synthesis of 2-(sulfonylimino)-4-(alkylimino)azetidine derivatives.

[reaction: see text] Under very mild conditions, functionalized 2-(sulfonylimino)-4-(alkylimino)azetidine derivatives were prepared in good to excellent yields via a copper-catalyzed multicomponent reaction of readily available terminal alkynes, sulfonyl azides, and carbodiimides without the assistance of a base. The mechanism may be through a [2 + 2] cycloaddition.

Iron-catalyzed homocoupling of bromide compounds.

The homocoupling of bromide compounds was successfully performed in one pot by a combination of metallic magnesium and a catalytic amount of iron salts. The binary catalytic system differentiates itself from other homocoupling reactions catalyzed by iron salts in that it requires neither the in situ preparation of Grignard reagent nor the addition of a 1,2-dihalogen compound as an oxidant. Various aromatic and alkyl bromides underwent the homocoupling smoothly affording the corresponding symmetrical hydrocarbon compounds in moderate to excellent yields.